The resurgent tuberculosis epidemic has arisen because of the HIV-1 epidemic. CD4+ T cells appear to play a major role in the defense against tuberculosis. A better understanding of the immune response to tuberculosis may lead to the development of adjunctive therapy to modulate host defenses and improve outcome. In animal models of tuberculosis, a T helper 1 (Th1) response characterized by IFN-g and IL-2 release, but no IL-4 or IL-5 release, correlates with an auspicious outcome. We hypothesize that an imbalance of the Th1/Th2 response is important in the pathogenesis of tuberculosis. To test this hypothesis, we will use the powerful research tool of bronchoalveolar lavage (BAL) to obtain cells from tuberculosis-involved and -uninvolved lung segments for cytokine assessment. We will evaluate IL-2, IFN-g, IL-4 and IL-5 using ELISA kits for BAL cell supernatants and BAL fluid. We will assess individual cells and cell types by in situ hybridization, immunohistochemistry and three-color flow cytometry for intracellular cytokines. We will determine the optimum method for characterizing the Th1 response in the lung. Both spontaneous release and gene expression for the Th1/Th2 cytokines will be assessed. We will thus be able to determine if the Th1 response truly controls the host response to M. tuberculosis and whether an altered or lack of Th1 response correlates with disease. The lab will be used for oligonucleotide synthesis, BAL processing, RNA isolation, ELISA, PCR analysis, in situ hybridization, laminar flow hoods, sample storage.